Sampling considerations for a potential Zika virus urosurvey in New York City.

In 2016, imported Zika virus (ZIKV) infections and the presence of a potentially competent mosquito vector (Aedes albopictus) implied that ZIKV transmission in New York City (NYC) was possible. The NYC Department of Health and Mental Hygiene developed contingency plans for a urosurvey to rule out ongoing local transmission as quickly as possible if a locally acquired case of confirmed ZIKV infection was suspected. We identified tools to (1) rapidly estimate the population living in any given 150-m radius (i.e. within the typical flight distance of an Aedes mosquito) and (2) calculate the sample size needed to test and rule out the further local transmission. As we expected near-zero ZIKV prevalence, methods relying on the normal approximation to the binomial distribution were inappropriate. Instead, we assumed a hypergeometric distribution, 10 missed cases at maximum, a urine assay sensitivity of 92.6% and 100% specificity. Three suspected example risk areas were evaluated with estimated population sizes of 479-4,453, corresponding to a minimum of 133-1244 urine samples. This planning exercise improved our capacity for ruling out local transmission of an emerging infection in a dense, urban environment where all residents in a suspected risk area cannot be feasibly sampled.

Photorefractive keratectomy with an ablatable mask and rail system for simultaneous correction of myopia and astigmatism: preliminary results.

BACKGROUND: Alternative methods to correct myopic astigmatism with excimer laser surgery are being examined in an attempt to increase efficacy and reliability. One approach that is developing interest is the incorporation of a polymethylmethacrylate mask into the laser procedure. We examined the efficacy and safety of the Summit Apex Plus laser using a new ablatable mask and rail system. METHODS: Retrospective study based on follow-up of patients at 1 month (59 eyes), 3 months (37 eyes) and 6 months (24 eyes) at an eye laser centre in southern Ontario. Patients were recruited from 19 ophthalmic practices located primarily in the Niagara region and in western New York. Selected patients with naturally occurring myopia and astigmatism were treated with the Summit Apex Plus laser with the mask and rail system. Patients were evaluated for changes in refraction and visual acuity, and complications (including glare, haloes, haze and lines lost of best corrected visual acuity) were assessed. We calculated the surgically induced refractive change using the Holladay 10-step method. RESULTS: At 6 months the average residual sphere for the low myopia group (-7.00 dioptres or less) was -0.60 D and for the high myopia group (greater than -7.00 D) -0.61 D. This result was found to be both stable and accurate over the follow-up period. The cylinder component was reduced irrespective of the amount of preoperative myopia. Vector analysis showed that in most patients the correction of astigmatism was accurate, although slight undercorrection was observed. Complications were minimal, with few residual adverse effects at 6 months. INTERPRETATION: We found the mask and rail technique to be both effective and safe. Refractive change was stable and accurate, although astigmatism was slightly undercorrected. The procedure resulted in few complications, most of which resolved by 6 months.